The invention described herein relates generally to neutron detectors, and more particularly to neutron detectors of very high temporal resolution.
The time-dependent distributions of the neutrons produced by various fusion reactions, such as those utilized in inertial confinement fusion targets driven by lasers such as the Nova laser of the Lawrence Livermore National Laboratory, are very difficult to accurately measure because in many instances the fusion reactions persist for times no longer than about 50 to 100 picoseconds. The detectors conventionally used to measure neutrons are not fast enough to record temporal variations in neutron flux with the requisite time-resolution for these applications.
Wang in U.S. Pat. No. 4,404,470 issued Sept. 13, 1983 discloses a neutron streak camera having a cathode of neutron-sensitive material such as uranium dioxide which provides secondary electrons upon receipt of neutron flux from a point source. The cathode is curved so that the differences in arrival times of tne neutrons at the cathode are compensated for by the slower particle speeds of the secondary electrons.
Griffith et al in U.S. Pat. No. 4,381,454 issued Apr. 26, 1983 disclose a neutron dosimeter comprising a radiator layer containing material such as .sup.6 Li and .sup.10 B which, when subjected to moderate energy neutrons, produces alpha particles that produce tracks in an adjacent detecting sheet comprised of a material such as carbonate plastic.
Young in U.S. Pat. No. 4,365,159 issued Dec. 21, 1982 discloses a neutron detector comprising a lithium-6 foil which, when subjected to neutrons, emits or radiates charged particles that cause selective reactions in a gas mixture comprised of a counting gas which is readily ionized when charged particles pass through it. Monitoring equipment in contact with the gas mixture detects reactions taking place therein.
Bollen et al in U.S. Pat. No. 3,891,852 issued June 24, 1975 disclose irradiating an intensifying screen with neutrons and subjecting the resulting light pattern onto a photographic material. The screen incorporates a phosphor compound in which gadolinium is the host metal, and at least one other rare earth metal is present as a fluorescence activating metal.
Givens in U.S. Pat. No. 3,688,117 issued Aug. 29, 1972 teaches a borehole tool for obtaining a quantitative measure of the concentration of uranium in rock formations. The tool includes an accelerator-type neutron source which is periodically pulsed for the production of bursts of fast neutrons spaced in time. A thermal neutron detector is employed to detect neutrons resulting from the neutron fission of uranium. A second detector detects delayed radiation, such as beta rays, emitted from a known element when irradiated with neutrons from the accelerator-type neutron source. The recorded output of the second detector offers a representation of the quantity of neutrons produced by the accelerator-type neutron source. The neutron bursts produced by the accelerator-type neutron source have a time duration on the order of a few microseconds or less.